1. FIELD OF THE INVENTION
The present invention relates to a method and apparatus for magnifying an image, more particularly, a method and apparatus for magnifying an image data stored in an image memory and restoring the magnified image data into the image memory.
2. DESCRIPTION OF PRIOR ART
FIG. 1 shows a typical image editing apparatus for performing various functions such as composition, rotation, edition and magnification of an image.
The image editing apparatus 51 is connected to an external image inputting unit 49 such as an image reader and to an external memory unit 50 such as a hard disc unit. Image data from the external image inputting unit 49 and/or the external memory unit 50 is once stored into an image memory means (not shown) of the image editing apparatus 51. The stored data is read out for processing and is processed according to a designated function mode. The processed image data is displayed by an image displaying unit such as CRT and/or outputted to a printer 53 for printing an edited image. The designation of the function mode is done through a key board 54 and a CPU 55 provided in the image editing apparatus 51 controls operation thereof according to the designated function mode.
One type of the image editing apparatus does not provide a special buffer memory for processing image data of one frame other than the memory for storing image data of one frame.
In such an image editing apparatus, the magnifying of an image is done by reading out the stored image data in unit of one line sequentially from the memory, magnifying every one line data and restoring the magnified one line data into the memory. Upon restoring the magnified one line data in the memory, the position thereof can be altered in case of need.
However, this method has such a disadvantage that the stored original image is not necessarily reproduced faithfully during the magnification thereof. This is because one line data to be read out may not necessarily contain the original line data to be magnified in the case that the magnified data is restored at the position of the original line data to be read out for magnification.
FIG. 13 shows an example wherein the faithful magnification of the original image is impossible.
Assume that an image on an area A is magnified twice onto an area B including the area A. When the magnification process is started, the image of the area A is read out in unit of one line from the top line A.sub.1 and magnified to restore it onto each line of the area B from the top line B.sub.1. If the i-th line data A.sub.i is magnified in the state that the (i-1)-th line data B.sub.i-1 is overlapped to the (i-2)-th and (i-1)-th line data A.sub.i-2 and A.sub.i-1, the magnified i-th line data B.sub.i is restored overlapped to the i-th and (i+1)-th line data A.sub.i and A.sub.i+1.
Due to this, the (i+1)-th line data A.sub.i+1 is altered or rewritten by the image data of the line B.sub.i. Thus, the line data of the original image data after the line A.sub.i is destroyed and, therefore, the faithful magnification of the original image data becomes impossible after the line A.sub.i.
This disadvantage can be avoided by using another memory having a capacity of one frame data for processing the latter. However, this method pushes up the cost of the image editing apparatus since another memory of a large capacity is needed.